Hydrodynamic Properties of Magnetic Nanoparticles with Tunable Shape Anisotropy: Prediction and Experimental Verification
Hydrodynamic Properties of Magnetic Nanoparticles with Tunable Shape Anisotropy: Prediction and Experimental Verification
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DOI：
10.1021/jp2078264
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发表时间：
2011-12-15
影响因子：
3.3
通讯作者：
Schurtenberger, Peter
中科院分区：
文献类型：
--
作者：
Martchenko, Ilya;Dietsch, Herve;Schurtenberger, Peter
我们描述的各向异性磁性纳米粒子的流体动力学特性的表征使用的组合，透射电子显微镜（TEM）和动态以及去偏振动态光散射（DLS/DDLS）。所使用的颗粒几乎是单分散的赤铁矿纺锤体，平均长度为280 nm，短轴为57 nm，涂覆有一层厚度可变的二氧化硅，使我们能够在5和2之间调节颗粒的纵横比。因此，它们的几何尺寸可以很容易地从TEM定量确定。此外，它们的尺寸对于采用DLS和DDLS来测量平移和旋转扩散系数D-T和D-R是理想的，而磁芯的存在为未来的研究和应用提供了大量的机会。我们证明，我们可以成功地预测的流体动力学性质的不同颗粒的TEM表征其尺寸分布的基础上，并使用已建立的理论模型的各向异性颗粒的流体动力学性质。当与理论预测相比，我们的光散射测量是在定量协议。这种理论和实验之间的协议是实现，而不必调用任何可调的自由参数，作为TEM结果被用来计算相应的扩散系数的绝对尺度上，我们证明，这是由于一个新的和简单的方法，统计加权的TEM信息，并使用正确的流体动力学模型所观察到的颗粒形状。此外，我们还证明了一个增强的灵敏度的旋转扩散的表面性质的椭球形纳米粒子，并指出，这可能是一个理想的工具，朝向表征功能化的表面。
We describe the characterization of the hydrodynamic properties of anisotropic magnetic nanoparticles using a combination of transmission electron microscopy (TEM) and dynamic as well as depolarized dynamic light scattering (DLS/DDLS). The particles used are nearly monodisperse hematite spindles with an average length of 280 nm and a minor axis of 57 nm, coated with a layer of silica of variable thickness that allows us to tune the particle aspect ratio between 5 and 2. Their geometrical dimensions can thus be determined easily and quantitatively from TEM. Moreover, their size is ideal to employ DLS and DDLS to measure the translational and rotational diffusion coefficients D-T and D-R, while the presence of a magnetic core opens a plethora of opportunities for future studies and applications. We demonstrate that we can successfully predict the hydrodynamic properties of the different particles based on a TEM characterization of their size distribution and using established theoretical models for the hydrodynamic properties of anisotropic particles. When compared with the theoretical predictions, our light scattering measurements are in quantitative agreement. This agreement between theory and experiment is achieved without having to invoke any adjustable free parameter, as the TEM results are used to calculate the corresponding diffusion coefficients on an absolute scale We demonstrate that this is achieved due to a new and simple method for the statistical weighting of the TEM information, and the use of the correct hydrodynamic models for the observed particle shape. In addition, we also demonstrate an enhanced sensitivity of the rotational diffusion for the surface properties of ellipsoidal nanoparticles, and point out that this may serve as an ideal tool toward characterizing functionalized surfaces.